Large-scale commercial production of proteins, such as antibodies, typically relies on expression of the protein by cultured eukaryotic cells. In general, it is recognized in the art that increasing mRNA copy number results in increased protein expression. Additionally, bioactive RNAs such as silencing RNAs (siRNA) are useful to prevent the expression of genes that produce undesired effects in cells. Large-scale production of proteins by cultured eukaryotic cells and bioactive RNA technologies are both dependent on the efficient transcription of genes into RNA encoding proteins or bioactive RNAs, respectively. However, low protein expression or low RNA transcript levels are common problems encountered in the use of these technologies.
The OCT-2 protein and its known homologs are transcription factors capable of increasing the production of RNA transcripts from genes responsive to this protein. The predominant, bioactive form of Homo sapiens OCT-2 (SEQ ID NO: 2) consists of 463 amino acid residues and contains an inhibitory domain, a DNA binding domain, and an activation domain (FIG. 1). The DNA binding domain of the OCT-2 protein binds the “octamer site” having the consensus sequence 5′-TNATTTGCAT-3′ (SEQ ID NO: 15; where N is any nucleic acid residue) in the promoter or regulatory region of OCT-2 responsive genes. See Müller et al. in Nature 336: 544 (1988). After DNA binding, the activation domain of the OCT-2 protein is believed to interact with the Homo sapiens co-activator protein OBF-1 (SEQ ID NO: 8) to stabilize formation of an active RNA polymerase II protein complex that can produce RNA transcripts. See Boss, Current Opin. In Immunol. 9: 107 (1997). The activity of OCT-2 increases the rate of formation of active RNA polymerase II protein complexes resulting in an increase in the production of RNA transcripts from OCT-2 responsive genes.
Genes may be naturally OCT-2 responsive or engineered to become OCT-2 responsive by inserting an “octamer” DNA sequence into the promoter or regulatory region of the gene. Consequently, it is expected that low levels of protein expression or low bioactive RNA levels could be increased by overexpressing OCT-2 alone or with the OBF-1 coactivator protein to increase transcription of OCT-2 responsive genes. Thus, a need exists for novel OCT-2 compositions and effective methods for increasing the expression or transcription of OCT-2 responsive genes.